Gemcitabine and Oxaliplatin(GemOx) shows effective activity in patients with relapsed diffuse large-cell lymphoma and other solid tumors. Our Previous study showed that two-weekly regimen of rituximab combined with GemOx regimen acheived comparable response rate to R-miniCHOP.The investigators therefore design this open-label,phase III and random trial to compared the safety and efficacy of R-Gemox versus R-miniCHOP as first-line treatment of elderly patients with diffuse large B cell lymphoma.